The sales appear to represent a significant portion of Gore's stake in the iPhone maker. According to the most recent Apple proxy statement, filed in January, Gore's ownership in Apple is roughly 721,000 shares.

But that figure includes stock options for roughly 276,000 shares scheduled to vest on February 1. It's not clear if Gore has exercised his option to acquire those shares.

In the event that Gore has not exercised the new slice of options, his stock sale this week would account for half of his stake in Apple.

Gore serves as a member of Apple's board of directors. Friday's SEC filing does not mention Gore's stock sales being part of a so-called 10b5-1 plan, the trading plans that company insiders typically use to sell shares at regular, pre-determined intervals.